1. Field of the Invention
The present invention relates to a high speed and precision electron beam drilling apparatus for drilling holes in a substrate, especially a substrate for an electronic equipment which need a number of high density drilled holes.
2. Description of the Prior Art
In recent years, hard-to-work material such as refractory alloy or ceramics has been widely used. Such a material is hardly machined by a conventional method. For example, an LSI chip mounting substrate used in an electronic computer is made of an alumina plate of approximately 100 mm square in which approximately 40,000 small holes having a diameter of 0.1 mm-0.15 mm are arranged. Such small holes are mostly arranged without regularity and directivity. Such an alumina substrate is machined by drilling holes by a drill or an electron beam by positioning it to respective hole positions, or drilling uniformly distributed holes by a pressing mold and clogging undesired holes. In the former method, a speed and an acceleration/deceleration of a drive mechanism on which the substrate is mounted are limited and hence an operation speed is limited. Accordingly, when the number of holes to be drilled is large, a long time is required to machine each substrate. In the latter method, the manufacture of the mold is expensive and the clogging of the undesired holes needs a lot of tasks.
In general, in order to drill holes at a high speed with a various patterns, a system which can be positioned at a high speed and can drill holes at a high speed is needed. For this purpose, it is possible to fix the substrate and control deflection of a high energy electron beam to drill the holes. However, it is difficult to precisely control the deflection of the high energy electron beam over a wide range and it is not applicable to the drilling of the substrate of the electronic equipment in which the range of the drilling spreads relatively widely.